This invention relates to oxidation of alkanes using metalloporphyrins as catalysts, and more particularly to such processes in which nitro groups have been substituted for hydrogen in the porphyrin ligand.
The use of metalloporphyrins as catalysts for the oxidation of hydrocarbons with air in the liquid phase has been shown in our U.S. Pat. Nos. 4,895,680 and 4,895,682 with the further finding that halogenation of the porphyrin ring led to even more active and stable catalysts (our U.S. Pat. Nos. 4,900,871 and 4,895,682 and pending application Ser. No. 568,118 filed Aug. 16, 1990). Since these discoveries we have been able to correlate increased electron withdrawal from halogenation of the porphyrin ring to increased catalytic air oxidation activity. J. E. Lyons and P. E. Ellis, Jr., Catalvsis Letters 8, 45 (1991).
It is also known that other functional groups besides halogens can lead to electron withdrawal in porphyrins. For example, L. C. Gong and D. Dolphin in Can. J. Chem., 63, 401 (1985) found that successive nitration at the meso positions of Zn(octaethylporphine) eventually giving Zn(mesotetranitrooctaethylporphine) led to more easily reduced porphyrins, evidence for electron withdrawal from the ring. Other workers such as Catalano, et.al. in J. Chem. Soc., 1535 (1984) have been able to nitrate the beta or pyrrolic positions in various metal tetraphenylporphyrins.